1. Field of the Invention
The present invention relates to the field of ornamental landscaping and, in particular, to a filter system designed to efficiently remove solid wastes and biologically decompose suspended wastes in fish ponds.
2. Description of the Related Art
Fish ponds accumulate and generate a variety of contaminants and waste products that must be removed and treated to maintain the attractive appearance of the fish pond and the health of the fish living therein. The exposed water surface tends to retain air blown dust, dirt, and leaves and other plant matter that falls in. The fish themselves produce excrement that is a solid waste material and a source of unwanted biological activity. The temperate closed water ecosystem that is essential for the fish is also an excellent environment for the growth of algae and other undesirable living organisms. Fish food that remains uneaten by the fish can contaminate the pond and nourish undesirable living organisms. The closed system of a fish pond also favors chemical processes such as ammonia production that, if left unchecked, can rapidly degrade the appearance of the fish pond and its ability to support healthy fish.
The accepted method of maintaining the health and appearance of a fish pond is to separate the solid waste from the water, react the chemicals to either remove them or make them non-damaging, and treat the water to kill undesirable organisms. Two methods have typically been used to do this. One is to filter out the solid wastes and dispose of them, treat the water with a variety of chemicals and/or high intensity UV light to kill biological undesirables, and react the undesirable chemicals. The other is to employ a filter medium that retains the solid waste and decomposes the waste with biologically active bacteria that live on the filter medium. This method would also typically require treatment with high intensity UV light or chemicals to eliminate the undesirable biological and chemical constituents, although the chemical and/or UV light treatment regimen may not be as rigorous as with simple filtering.
A variety of methods and apparatuses are known to remove solid material from a liquid, however a major concern with removal of solid waste is what to do with the waste once it is separated from the water. Separation devices that depend on density differences, such as a centrifuge, are not effective in fish pond applications because many of the waste solids are approximately the same density as the water they are in, therefore the effective devices typically employ some type of filtering to trap the solids. The two major ways to handle the separated waste are to discard the waste trapped in a filter along with the filter or to backwash the filter and direct the waste stream elsewhere. A disadvantage of removing the waste trapped in a filter along with the filter is that generally these types of filters are a single use filter and thus must be replaced with a new one when the old one is full. It can be appreciated that the labor and cost to perform this replacement would be a drawback to a user for which the fish pond is a decorative and recreational item.
In order to avoid the cost and inconvenience of changing filter elements, the preferred method of removing trapped waste is to utilize some form of backwashing. Backwashing essentially consists of reversing the direction of water flow in the filter and thereby forcing the waste products out a waste outlet. The filter media does not typically need to be removed and after the backwashing is complete, the filter media is ready to retain more waste. Advantageously, fish ponds are often located adjacent garden areas and the backwashed water contains partially decomposed fish and vegetable waste that makes a beneficial fertilizer in the garden. However, the water discharged in the backwashing procedure is typically a cost to the user and minimizing water discharge is a concern particularly in areas where water is in limited supply.
The biological reaction process is an advantageous adjunct because the heterotrophic bacteria that perform the reaction are naturally occurring in the pond water. No user action is needed to establish and maintain a colony of beneficial bacteria other than to provide a place for them to live. Also, biological reaction converts many of the undesirable chemicals to non-harmful forms and thus reduces the need for chemical treatment. The chemicals used for chemical treatment are relatively expensive and many users would understandably like to minimize their handling of chemicals. The heterotrophic bacteria are not suited to live freely suspended in water and require a surface on which to grow. This has typically been done on the filter medium which generally consists of a gravel bed or filter mat.
A disadvantage to biological reaction is the relatively large amount of reactor volume and time typically required for the process to occur. With traditional gravel or filter mats, a biological filter/reactor can require a filter/reactor volume of up to 40% of the volume of the pond itself. It can be appreciated that such a large filter/reactor assembly is expensive to purchase and install and can negatively affect the aesthetics of the fish pond system. In addition a traditional biological reaction filter design can require several weeks to several months for the bacteria to substantially decompose the deposited wastes. The time required for waste decomposition must be such that the waste is decomposed at at least the rate it is deposited. Otherwise the filter becomes overloaded and can no longer protect the health and appearance of the pond.
As the bacteria live on a solid surface, there is an upper limit to how many can live on a given area, i.e. their population density. The time and volume required for a biological reaction filter can be dramatically reduced by providing increased area for the bacteria to live on and thereby increasing the number of bacteria resident in the filter reactor. The optimal filter media provides the highest surface area-to-volume ratio possible. With gravel or fibrous mats, the bacteria live on the surface and from a consideration of the shape of a piece of gravel or fiber it can be seen that other configurations of filter media would provide greater surface area for a given volume of media.
One type of filter media on the market with a higher surface area to volume ratio than gravel or fibers is the ACE-1400 media. The ACE-1400 media is made of plastic tubing with a specific gravity slightly less than one, which is cut to be slightly longer than the diameter of the tubing. The ACE-1400 is approximately 3.5 mm in diameter and 5 mm long. It can be appreciated that a hollow tube can support bacteria on both the outer and the inner surface. The size and shape of the hollow tube media is such that it has 15 to 20 times the surface area of an equivalent volume of gravel or fiber matting.
The ACE-1400 type media is typically placed in a container and pond water is pumped through the container so as to flow generally upwards. Since the ACE-1400 media has a specific gravity slightly less than one, the media floats towards the top of the container. Since the pond water is generally flowing upwards in the container, waterborne waste material is trapped throughout the media, but predominantly towards the bottom. The naturally occurring bacteria reside on and within the ACE-1400 media and digest the waste that lodges within the media.
The container is also provided with valves and piping to backwash the container periodically by reversing the water flow direction downwards and then out of the container. The backwashing causes the media to swirl and tumble, thereby releasing trapped solids. A properly sized container filled with the appropriate amount of media would generally require backwashing once a week. The container is provided with screens so that the media does not escape the container during either backwashing or normal operation. The filter system is also provided with screens to restrict larger solids such as leaves, twigs, and fish from being pumped into the filter container.
It can be appreciated that the more media that is in a filter system, the more surface area is provided for heterotrophic bacteria growth. However, because the ACE-1400 filter media is of a uniform size and shape, movement of the water tends to cause the filter elements to stack in a uniform manner, particularly when the container is filled to a relatively high percentage of capacity. The stacking process tends to create channels or voids in the filter media. These channels provide paths for the water to flow along without requiring that the water pass through the filter media. It can be appreciated that the filter is not effective in trapping and decomposing wastes if the water is not passing through the media. The stirring motion of backwashing randomizes the orientation of the filter elements, however they tend to re-stack and create channels in a relatively short time after the system returns to normal filtering flow.
While the ACE-1400 filter media and system offer advantages over traditional disposable filters and chemical treatment or gravel or fiber matting filter systems employing biological waste decomposition, it can be appreciated that improvements upon this system would be an advantage to the users of fish ponds. It can be appreciated that there is an ongoing need for a filter system for fish ponds that employs naturally occurring bacterial metabolization of wastes to remove these wastes from fish ponds. The system should be economical to purchase and install. The filter media should be reusable and provide the maximum surface area to volume ratio possible to support a maximum number of beneficial bacteria and to enable the system to be sized as small as possible and decompose the solid wastes as rapidly as possible. The system should require minimal use of chemicals to treat the water. The backwashing method should be as efficient as possible to remove the maximum amount of waste and extend the periods between backwashes, while avoiding channeling effects and corresponding failure to filter.
The aforementioned needs are satisfied by the fish pond filter system of the present invention, which in one aspect is a novel filter media with an increased surface area-to-volume ratio. In another aspect, the invention is a filter reactor with a more efficient backwashing system.
The extruded bio-tube filter media of the present invention is formed from extruded ABS plastic with a specific gravity slightly greater than one. The extruded bio-tube is generally tubular with internal and external ribbing. The addition of the internal and external ribbing provides approximately twice the surface area for the bio-tube of the present invention compared to a similar sized simple tube media, such as the ACE-1400. In addition, the internal ribbing provides smaller interior passages and allows the media to trap proportionally smaller waste material.
An additional advantageous feature of the present invention is that the media is provided in several different sizes. Also, the present invention is sized so as to be generally 1.3 times as long as it is in diameter. The differing sizes and the shape of the media of the present invention inhibit uniform stacking of the media material. Since the media cannot readily stack together in a uniform fashion, channeling of the material is also inhibited.
In another aspect of the invention, an efficient backwashing system is provided. The system includes jets adapted to create a vortex within the filter media container during the backwashing operation. The vortex created more efficiently dislodges accumulated waste material and directs the dislodged waste and carrier water out a waste pipe. The vortex created within the fish pond filter system of the present invention more completely cleans the filter media in a shorter time and requires less water to do so. Thus, the fish pond filter system saves time and money. These and other objects and advantages of the present invention will become more fully apparent from the following description taken in conjunction with the accompanying drawings.